John Deere 4840 no hydraulics, no steering, no brakes. How to solve this problem?
There are some very simple items to check to verify the problem. First, the problem was a gradual failure or an instantaneous failure. That will tell you if something is worn or if something broke. Second, connect a pressure gauge to the filter relief valve housing.
You are checking to see if your lube / charge pump is pulling something out. If you see pressure, check the pressure on your main hydraulic pump. If pressure goes to the main hydraulic pump but nothing comes out, remove the pressure relief valve from the system and inspect it for clogging or wear. If the valve is okay, connect a flow meter directly to the outlet of the pump to see if the pump is pumping anything.
The pump may be worn. Now if you don’t have any pressure on the charge pump, take the plug out of the filter box and have someone hold a bucket in the hole and start the tractor, if nothing comes out, check the pickup screen before it the bomb is doomed. If the screen is clean as was the case on a tractor that I made recently, then you have to break it at the rear of the tractor.
The charge pump is located on the rear axle. You cannot just order a new pump. You have to order the specific parts you need. To get to the pump you have to remove the cover of the rock shaft box which is a long process. The hole work including making the special tools to lift the cover will take 20-25 hours to complete. In my case the pump was fine but there was a huge hole in the pump outlet tube.